1. Field of the Invention
The present invention generally relates to a method for fabricating microelectronic or micro-optical devices or components, including thin film magnetic heads, on a substrate. More specifically, the present invention relates to a chemical-mechanical contouring (CMC) method for forming a locally contoured surface on a thin film substrate.
2. Description of the Related Art
Chemical-mechanical polishing (CMP) is a known technique for planarizing various structures on a thin film substrate. CMP is conventionally used to create a smooth, planar surface for intermediate processing steps of a thin film fabrication process. Specifically, various layers such as metallization layers are deposited and etched during the fabrication of thin film devices on a substrate. These layers are commonly subjected to CMP so that planar deposition of additional layers is achieved. CMP processing not only is used to planarize protruding surfaces, but also to remove undesirable residues that remain from other substrate processing steps.
CMP involves simultaneous chemically etching and mechanical polishing or grinding of a surface so that a combined chemical reaction and mechanical polishing removes a desired material from the substrate surface in a controlled manner. The resulting structure is a planarized substrate surface with protruding surface topography leveled. CMP is typically performed by polishing a substrate surface against a polishing pad that is wetted with a slurry including an acidic or basic solution, an abrasive agent and a suspension fluid.
Thin film magnetic heads, which are constructed using advanced integrated circuit processing techniques, have been developed to improve performance of high density magnetic recording while reducing fabrication cost. Thin film magnetic heads are typically constructed using multiple substrate processing steps, including steps of deposition, etching and planarization of multiple insulative, conductive and magnetic layers. In a typical conventional thin film magnetic head fabrication process, on the order of thousands of thin film heads are formed on a six inch substrate. The substrate is subsequently diced into a large number, typically thousands, of individual thin film heads. Each head is mounted individually, one-by-one on a head mounting block. Each mounted head is subjected to a lapping process to planarize each head, resulting in a planar, rectangular parallelepiped structure. Lapping is a method of reducing the thickness of a substrate slice for applications in which accuracy of the substrate thickness is important to the operation of the device. After lapping processing, a slurry of water and fine grit is used to wear down the back of the slice. The slurry is placed between a flat plate and the back of the slice and the slice is moved with respect to the plate to mechanically remove the substrate material.
The individual lapping of each thin film magnetic head, one-by-one, is tremendously time consuming, greatly raising the cost of each thin film head and the cost of a recording and playback apparatus using thin film heads.
In some processes, the thousands of thin film heads are constructed using multiple processing steps, similar to the processing steps of integrated circuit manufacture. The substrate is then sliced into rows to produce strips typically holding ten to sixteen devices. A row tool is the used, applying a rocking or lapping motion to planarize the multiple heads in a row, resulting in the planar, rectangular parallelepiped structure. The procedure of slicing the substrate into rows greatly improves processing as compared to the alternative of processing each head individually. One disadvantage of this procedure is that the step of slicing the substrate into rows for lapping using a row tool is an extra step that increases manufacturing time and costs.
A disadvantage of the conventional thin film magnetic head having a planar, rectangular parallelepiped structure is that this structure does not furnish an optimum contact of the magnetic tape media.
What is needed is a thin film magnetic head planarization technique which avoids planarization of each head individually. What is further needed is a thin film magnetic head fabrication technique that produces a thin film magnetic head having an improved tape contact.